We all have our favorite Emacs packages. I’ve written about mine a few times (1, 2, 3). A few packages make almost everyone’s list. There’s Magit and Org-mode, of course. Many people say at least one of those is the reason that they use Emacs. Another common favorite is which-key. If you’re not using it, you should be.
Bozhidar Batsov has his own favorites list. He limited himself to five packages but even so his list and mine have significant overlap. He also has an “Honorable Mentions” list that provides even more overlap.
Our biggest disagreement is on the Swiper/Counsel package. Oddly, he likes Ivy but uses Swiper and Counsel so seldom that he’s switched Ivy out for Selectrum, a lighter weight Ivy-like package that doesn’t include the Swiper and Counsel functionality. Outside of Org-mode, the Ivy/Swiper/Counsel package is my most important. I use it hundreds of times a day and my workflow absolutely depends on it.
Of course, that’s the fun of these lists: you get to see what other people think is important and maybe learn about a useful package you weren’t using. In any event, it’s always worthwhile listening to what Batsov thinks is important so take a look at his post if you haven’t already.